Center for Tropical Research
Institute of the Environment and Sustainability
University of California, Los Angeles

Research Interests

My main interest is studying the factors promoting avian diversity in South America. Specifically, I study phylogeographic patterns of hummingbird species in the Andes and Yellow Warbler populations in the Galápagos Islands, paying particular attention to the role of geography, natural selection, and genetic drift in differentiation.

The impressive latitudinal range the Speckled Hummingbird (Adelomyia melanogenys) exhibits (from the Andes of Venezuela to Bolivia) makes it suitable to examine mechanisms promoting genetic and morphologic differentiation in the different habitats where it is found along the cordillera and at different elevations. To conduct these studies, I use a combination of methods from morphometrics, multilocus phylogenies, and remote sensing data.

In contrast to the examination of evolutionary aspects of diversification in the Andes, I am also interested in patterns of recent differentiation in the Yellow Warbler subspecies (Dendroica petechia aureola) from the Galápagos and Cocos Island. I expanded on the Yellow Warbler phylogeny, including samples from these islands to determine lineage relationships as well as to reconstruct migration and colonization routes.

Evolutionary Patterns of Diversification in the Andean Hummingbird Genus Adelomyia

One part of my doctoral research looked into the patterns of genetic diversity and morphological variation in Adelomyia hummingbirds. The six monophyletic clades recovered have lineage limits at well-defined geographic barriers indicating the important impact of geographic isolation on genetic diversification. In contrast, morphological analyses suggested that, despite deep genetic breaks, ecology was important in promoting differentiation. The combination of morphometrics, multilocus phylogenies, and remote sensing data proved to be a useful tool in informing speciation patterns of diversification in Adelomyia.

Subspecies Adelomyia melanogenys melanogenys from east Ecuadorian and Peruvian Andes (A),A. m. maculata from west Ecuadorian Andes (B), and A. m. inornata from the Andes of Bolivia (C)

I also examined patterns of recent differentiation in the yellow
warbler subspecies (Dendroica petechia aureola) from the Galápagos and
Cocos Island. Bayesian Inference analysis suggests aureola yellow
warblers diverged from Central American lineages 300,000 years ago
colonizing the Pacific islands through the Galápagos first and back to
the Cocos Island. Within the Galápagos archipelago patterns of genetic
variation in microsatellite and mitochondrial markers suggested
prevailing current wind patterns may play a role in structuring
populations across islands. No intra-island patterns of morphological
variation were found, even across step ecological gradients,
suggesting that either (i) high levels of gene flow may be
homogenizing the effects of selection, (ii) populations may not have
had enough time to accumulate the differences in morphological traits,
or (iii) yellow warblers show lower levels of ‘evolvability’ than some
other
Galápagos species. Thus, by incorporating genetic data and
morphological variation these results provide an understanding of
microevolutionary processes occurring in island forms.

Speciation Modeling and Conservation

In collaboration with the NASA/Jet Propulsion Laboratory, I am generating distributional images which will contain patterns of genetic diversity, morphological differentiation, and physiological adaptation to examine the underlying effects of the various mechanisms responsible for the patterns observed and relate them to detailed habitat characteristics and to geography. I will be able to identify particular geographical regions and gradients where these differentiations and adaptations are produced and maintained and where conservation efforts should be allocated to preserve evolutionary processes in the Tropical Andes region.

Ecological modelling for the Speckled Hummingbird in Ecuador based on various climatic and environmental variables from satellite data

The Effects of Elevation on Flight Mechanics

Elevational gradients are of particular interest to me because they present a unique scenario where different selection regimes can act within relatively short distances, creating a mosaic of selecting agents as one examines populations up and down the gradient. In particular, I am interested in the effect of elevation on the flight mechanics of the hovering flight of the Speckled Hummingbird. In my past research, I have found that hummingbirds at higher elevations, such as 3000 m, modulate their flight as a response to the hypoxic and hypobaric conditions, compared to a the lower energy hovering flight of their conspecifics at lower elevations.

Flight ecophysiology of the Speckled Hummingbird

Cloud Forest in Manu National Park, Peru

In a 2011 publication in the Journal of Global Change Biology, written in collaboration with other researchers, we showed that Neotropical hummingbirds are expected to shift altitudinally upwards in the Andes in response to climate change, which is predicted to influence their flight performance.

Publications

Chaves, J.A., P.G. Parker, and T.B. Smith. 2012. Origin and population history of a recent colonizer, the yellow warbler in Galapágos and Cocos Islands. J. Evol. Biol. 25: 509-521. PDF.

Web Contributions

Some of my illustrations from the plates of the field guide, Aves Comunes de Otonga y los Bosques Nublados Noroccidentales del Ecuador (English translation: Common Birds of Otonga and the Cloud Forests of Northwestern Ecuador).

The Center for Tropical Research, located on the third floor of La Kretz Hall, is part of the Institute of the Environment and Sustainability at the University of California, Los Angeles. For general inquiries, contact Christa Gomez, CTR Office Manager, at 310-206-6234, or by email at cgomez@lifesci.ucla.edu. Visitors are always welcome.